1. Field of the Invention
The present invention relates to a thread cutting device for sewing machine used when a sewing operation is performed while inserting an elastic cord in a circular part of a sewing object such as a waist part of underwear.
2. Description of the Background Art
Referring to FIG. 10, for example, in the case that the operator performs a sewing operation while inserting an elastic cord into a waist part (circular part) 51 of a sewing object 50, such as underwear, by using a multi-needle sewing machine, the operator performs the sewing operation while moving the waist part 51 in a direction indicated by arrow A, in the state that the edge of a looper thread is held by a looper thread end holder disposed in the inside of a sewing bed. As the result, a plurality of seams 52 are formed throughout the periphery of the waist part 51.
In this sewing operation, at the completion of the sewing throughout the periphery of the waist part 51, the looper thread is hung on a thread guard part disposed at the tip of a movable thread guard member moved to the underside of an needle location. With the retraction of the movable thread guard member in this state to a side orthogonal to a sewing direction with respect to the needle location, the looper thread hung on the thread guard part is pulled into a preset position and then cut at this setting position by mutually contact action between the movable thread guard member and a stationary blade member, and the vicinity of a cutting edge of the looper thread is nipped between the movable thread guard member and a thread nip member in the looper thread end holder, then entering the state of waiting for the next following sewing operation.
In the sewing machine provided with the above-mentioned thread cutting device, a looper thread end 52c, so-called xe2x80x9cfluff,xe2x80x9d remains (normally, as long as about 5 cm to 7 cm) at a starting position 52a of the seams 52, because the next sewing operation is started in the state that the vicinity of a cut end of the looper thread is nipped between the movable thread guard member and thread nip member. In order to eliminate such a long looper thread end 52c, i.e., fluff, the operation must cut off by manual operation with scissors etc every time the sewing operation is completed. This manual operation is time consuming, thereby lowering the sewing efficiency and increasing the sewing cost. In addition, there is the problem of imposing on the operator the serious burden if the operator continuously sews a large number of sewing objects one after another.
It can be considered that in order to omit the operation of fluff removal, part of the remaining long looper thread end 52c is sewed into the seams 52 in the following manner that the staring position 52a and a termination position 52b of the seams 52 are sewed one over the other. However, in this manner, the looper thread end 52c is extremely unstable and likely to drift during the time of sewing, failing to exactly match the seams 52. This produces a poor finish on the sewing product, leading to non-conforming article. Consequently, the fluff is usually removed by manual cutting that is time consuming and imposes on the operator the serious burden.
As means for omitting such fluff removal by manual cutting, there have been proposed the followings.
Firstly, in a device disclosed in Japanese Patent Publication No. 7-34838 (hereinafter referred to as xe2x80x9cdevice Xxe2x80x9d, concurrently with, alternatively, immediately after a sewing operation is started in the state that the vicinity of a cut end of a looper thread is nipped by a movable thread guard member and a thread nip member that constitute a lower thread (looper thread) retainer, the cut end of a looper thread is pulled into seams so as to reduce the edge length of the looper thread projecting from the starting position of the seams in the following manner that a stationary blade member and thread nip member are further retracted in a direction in which they depart from a setting position retracted to a side of a needle location with respect to the needle location, in order to release the nipping of the looper thread cut end by the movable thread guard member and thread nip member.
Secondly, in a device disclosed in Japanese Patent Unexamined Publication No. 1-290571 (hereinafter referred to as xe2x80x9cdevice Yxe2x80x9d), concurrently with, alternatively, immediately after a sewing operation is started, a cut end of a looper thread is pulled into seams and the edge length of the looper thread projecting from the starting position of the seams is reduced in the manner that a movable thread guard member is allowed to approach a needle location side by a predetermined amount in order to release nipping of the looper thread cut end by the movable thread guard member and a thread nip member.
With a conventional thread cutting device for sewing machine having the construction as shown in device X or device Y, the fluff removal by manual cutting can be omitted by reducing the length of the looper thread end projecting and extending from the starting position of the seams. However, to device X, in addition to the functions required for a thread cutting device, such as the cutting of a looper thread when a sewing operation is completed; and the nipping of a looper thread end so cut, in preparation for the next following sewing operation, it is necessary to add the following special functions that the nipping of the cut end of the looper thread is released concurrently with or immediately after the sewing operation is started, and that in order to apply tension to the cut end and pull the edge of the looper thread into the seams, the stationary blade member and thread nip member are further retracted in a direction in which they depart from their respective setting positions with respect to the needle location, while the movable thread guard member is maintained in its setting position. It is therefore necessary to convert an existing thread cutting device throughout its structure, thereby complicating the structure and increasing the cost of the device.
In device Y, an existing thread cutting device can be used as it is. Further, the structure of device Y is simpler than that of device X, and it is easy to reduce the cost. It is however necessary to add to the existing thread cutting device such a construction that only the movable thread guard member is moved so as to approach the needle location side by a predetermined amount while the stationary blade member and thread nip member are maintained at their setting positions. Therefore, an increase in the cost of the device is unavoidable.
Additionally, the conventional thread cutting devices, such as device X and device Y, are of the type in which the nipping of the cut end of the looper thread is released at a position away from the side of the needle location, in order to pull the cut end into the seams. It is therefore unavoidable that a looper thread having a considerable length (i.e., fluff) remains and projects beyond the starting position of the seams, although no manual cutting may be required. A further reduction in the length of the remaining thread is therefore desired in the case of quality sewing product, and depending on the type of the sewing product.
It is an object of the present invention to provide a thread cutting device for sewing machine that can considerably reduce the length of a looper thread end remaining at a starting position of seams merely by adding a very simple construction to an existing thread cutting device.
According to a first aspect of the present invention, in a thread cutting device for sewing machine including a thread cutting device that immediately after a sewing operation is completed, cuts a looper thread after pulling it into a setting position located at a side orthogonal to a sewing direction with respect to a needle location of a throat plate, there is provided a nip means for temporally nipping and holding a cut end of the looper thread cut by the thread cutting device, in the vicinity of the setting position. A blade is fixed to the throat plate in a state that a cutting edge of the blade is faced to the needle location. The blade can cut, under sliding cont, a portion of the looper thread that is hung over between the nip means and the fabric with the feed of fabric immediately after a sewing operation is started in such a state that the cut end is nipped and held by the nip means.
With this construction, immediately after sewing operation is completed, the looper thread pulled into the setting position at a side of the needle location is cut by the thread cutting device, and the cut end of the looper thread so cut is temporarily nipped and held in the vicinity of the setting position by the nip means. When a sewing operation is started in this state and a fabric is fed, a portion of the looper thread hung over between the nip means and the fabric is cut under sliding contact by the cutting blade edge of the blade fixed to the throat plate, which faces to the needle location. Thus, the looper thread cutting immediately after the sewing operation can be performed by using the existing thread cutting device conventionally provided in sewing machines. On the other hand, when a portion of the looper thread hung over between the fabric and the nip means in the vicinity of the setting position is cut immediately after the next following sewing operation is started, it can be cut under sliding contact at a location extremely adjacent to the starting position of the seams by using the cut end facing to the needle location in the blade fixed to the throat plate. It is therefore possible to considerably reduce the length of the looper thread end remaining and projecting beyond the starting position of the seams, thereby eliminating fluff disposal by the operator""s manual cutting every time the sewing operation is completed. Further, unlike device X and device Y, there is no need for adding any additional function to the thread cutting device in order to reduce the length of the looper thread end remaining at the sewing start position. Only necessary work is to fix the blade to the throat plate. Therefore, as compared to device X and device Y, the overall construction of the device can be more simplified to reduce the cost.
According to a second aspect of the present invention, in a thread cutting device for sewing machine including (i) a movable thread guard member having at its tip a thread guard part that immediately after a sewing operation is completed, travels to the underside of a rectile location of a throat plate and picks a looper thread, the movable thread guard member retracting the thread guard part to a side orthogonal to a sewing direction with respect to the needle location and pulling the looper thread picked by the thread guard part into a setting position; (ii) a stationary blade member for cutting the looper thread pulled into the setting position by the movable thread guard member, under mutually sliding contact action with the thread guard part; and (iii) a thread nip member for nipping the vicinity of a cutting edge of the looper thread cut by the movable thread guard member and the stationary blade member, between the movable thread guard member and the thread nip member. In this thread cutting device, a blade is fixed to the throat plate in such a state that a cutting edge of the blade is faced to the needle location. The blade can cut, under sliding contact, a portion of the looper thread that is hung over between a fabric and the nipped cut end with the feed of fabric immediately after a sewing operation is started in such a state that the vicinity of the cut end of the looper thread is nipped between the movable thread guard member and the thread nip member.
With this construction, immediately after the sewing operation is completed, the movable thread guard member travels to the underside of the needle location and then retracts to a side orthogonal to the sewing direction in the state that the looper thread is hung on the thread guard part disposed at the tip of the movable thread guard member. Thereby, the looper thread is pulled into the setting position on a side of the needle location and then cut by the mutually sliding contact action between the thread guard part and the stationary blade member, and the cut end of the looper thread so cut is nipped and held between the movable thread guard member and thread nip member, in the vicinity of the setting position. When the sewing operation is started in this state and the fabric is fed, a portion of the looper thread hung over between a fabric and a nip position determined by the movable thread guard member and thread nip member is cut under sliding contact by the cutting blade edge of the blade fixed to the throat plate, which faces to the needle location. Thus, the cutting of the looper thread immediately after the sewing operation and the nipping of the cut end are performed by the movable thread guard member, stationary blade member and thread nip member, all of which are included in the existing thread cutting device of the conventional sewing machine. On the other hand, when a portion of the looper thread hung over between the nipped cut end and the fabric is cut immediately after the next following sewing operation is started, as in the case with the first aspect of the present invention, it can be cut under sliding contact at a location extremely adjacent to the starting position of the seams by using the cutting edge, facing to the needle location, of the blade fixed to the throat plate. It is therefore possible to considerably reduce the length of the looper thread end remaining and projecting beyond the starting position of the seams, thereby eliminating fluff disposal by the operator""s manual cutting every time the sewing operation is completed. Further, unlike device X and device Y, there is no need of adding any components for performing additional functions to the existing thread cutting device, in order to reduce the length of the looper thread end remaining at the sewing start position. Only necessary work is to fix the blade to the throat plate. Therefore, as compared to device X and device Y, the overall construction of the device can be more simplified to reduce the cost.
According to a third aspect of the present invention, the construction of the second aspect is usefully applicable to a thread cutting device for multi-needle sewing machine in which a plurality of needle locations in a throat plate are disposed in parallel in a direction orthogonal to a sewing direction, and a plurality of loopers corresponding to these needle locations are reciprocally movable in the direction orthogonal to the sewing direction. That is, in the case of so-called transverse looper type multi-needle sewing machine in which a plurality of loopers move reciprocally in a direction orthogonal to the sewing direction, there is a large distance between the needle location and a setting position at which the thread cutting device is retracted to a side away from the range of the loopers. This therefore increases the length of the looper thread hung over between the fabric and a nip position of the cut end of the looper thread. Even if added such a function as described in device X or device Y, there are limits to a reduction in the length of the looper thread end remaining. Whereas in the present invention, the cutting is executed at a locating facing to the needle location of the throat plate, so that the length of the looper thread end remaining can be reduced remarkably even in the transverse looper type multi-needle sewing machine.
According to a fourth aspect of the invention, in a thread cutting device, the cutting blade edge of the stationary blade is disposed, for example, so as to obliquely cross a needle location having a slender slot shape, and the cutting blade edge has a cutting width to tear a hang portion of the looper thread while the hang portion is allowed to slide along the cutting blade edge.
With this construction, the looper thread can be cut reliably, although the stationary blade tears it.
According to a fifth aspect of the invention, a thread cutting device includes a cut looper thread disposer having a thread suction device that sucks and holds, at a predetermined position before and after cutting, a portion of the looper thread to be cut by the stationary blade, and a thread pick and pull device that picks the portion of the looper thread and pulls it into a vicinity of a suction port of the thread suction device.
With this construction, the stationary blade can cut a plurality of looper threads collectively and reliably, without failing to cut some of the looper threads. In addition, waste thread occurred during the time of cutting can be sucked and collected into a specific location, so that the recovered waste thread is discarded.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.